CO20 CO 40 CO 80   Figure S1a: HR-TEM images and quantitative particle size distribution analysis of (A-B) CO20 ; (C-D) CO40 ; and (E-F) CO80 gold NPs. B A C D E F

B A C D E F HM15 HM35 HM75   Figure S1b: HR-TEM image and quantitative particle size distribution analysis of (A-B) HM15 ; (C-D) HM35 ; and (E-F) HM75 gold NPs.

HM15 HM35 HM75   S2a : CLS size distribution intensity curves. HM series

CO20 CO40 CO80   S2b: CLS size distribution intensity curves. CO series

CO20 CO40 CO80 Figure S3a: DLS size distribution intensity curves for the two sets of particles in water and CCM. CO series

HM15 HM35 HM75 Figure S3b: DLS size distribution intensity curves for the two sets of particles in water and CCM. HM series

Figure S4a, : CLS sedimentation times for HM set of NPs in water and CCM.

Figure S4b : CLS sedimentation times for CO set of NPs in water and CCM

Figure S5a: UV-vis absorbance spectra of the HM set of NPs measured in water and CCM.

Figure S5b : UV-vis absorbance spectra of the CO set of NPs measured in water and CCM

M CO20 CO40 CO80 CO20 CO40 CO80 kDa 201 126 91 39 32 17 t = 0 t = 72h M HM15 HM35 HM75 HM15 HM35 HM75 kDa 201 126 91 39 32 17 t = 0 t = 72 h Figure S6 : SDS page images of protein corona isolated from CO and HM series NPs at t = 0 and t = 72 hours.

HM15 HM45 HM75 HM15 HM45 HM75 M kDa 201 126 91 39 32 17 t= 0 t = 72 h conditioned CCM CO20 CO40 CO80 CO20 CO40 CO80 M kDa 201 126 91 39 32 17 conditioned CCM t = 0 t = 72 h Figure S7 : SDS page images of protein corona isolated from CO and HM series NPs at t = 0 and t = 72 hours. Cell culture medium was conditioned with A549 for 72 hours.

Figure S8 a: bright field image of A549 cell culture

Time (h) 0 1 3 6 20 24 28 44 48 52 68 72 Fig. S8 b: Fluorescence images of the cell monolayer stained by Hoechst/PI stained for viability and counting.

HM15 HM35 HM75 CO20 CO40 CO80 Fig. S8c. Cell monolayer integrity monitoring by statistical analysis of viability measurements of the cell monolayer exposed to different gold NPs. The ratio of living cells/ dead cells of the exposed A549 cells was analyzed with the IN Cell Analyzer 2200 in triplicates for each of the eleven time points.

HM 75 with cells 72 h HM 75 w.o cells 72 h CO80 with cells 72 h CO80 w.o cells 72 h Figure S9a: Raw UV-vis spectra measured for the CO80 and HM75 in CCM at different time points.

CO20 with Cells CO20 without Cells HM15 with Cells HM15 without Cells Figure S9b: Raw UV-vis spectra measured for the CO20 in CCM at different time points.

CO40 with Cells CO40 without cells HM35 with cells HM35 without cells Figure S9c: Raw UV-vis spectra measured for the CO40 and HM35 in CCM at different time points.

CO20 without cells CO20 with Cells 72 h 72 h CO40 with Cells 72 h CO40 without cells 72 h CO80 with Cells CO80 without cells 72 h 72 h Fig S10a: UV-vis spectra measured for all Co NP sizes. Each time point spectrum is an average of three different samples measurements..

HM15 with cells HM15 without cells 72 h 72 h HM35 with cells HM35 without cells 72 h 72 h HM75 with cells HM75 without cells 72 h 72 h Fig S10b: UV-vis spectra measured for all HM NP sizes. Each time point spectrum is an average of three different samples measurements.

Fig. S11 Number of cells per well plotted versus time point counted in automatic with the IN Cell Analyser 2200 Imaging System of the Hoechst stained nuclei from a square area of the bottom of the 96 well.

S12. SEM and EDX analysis Fig. S12a. SEM picture on the A549 cells treated with different NP sizes on the left. On the right are the EDX – Au maps for gold NPs from the selected regions of the SEM pictures.

Fig. S12b. SEM picture on the A549 cells treated with different NP sizes on the left. On the right are the EDX – Au maps for gold NPs from the selected regions of the SEM pictures.